1. Technical Field of The Invention
The present invention relates to a thermal power plant, and in particular, to a thermal power plant which can effectively treat a carbon dioxide gas discharged from a gas turbine.
2. Prior Art
In a conventional thermal power plant, for example, in a gas turbine plant or in a combined cycle plant combining a steam turbine plant and an exhaust heat recovery boiler into the gas turbine plant, an air is added in a gas turbine combustor to a fuel so as to generate a combustion gas, and then, such plants are driven by a thermal energy of the generated combustion gas. Moreover, the air is compressed by an air compressor so as to generate a highly pressurized air (high pressure air), and then, is used as an oxidizing agent for generating a combustion gas.
In such a thermal power plant, a natural gas, an oil gas, a coal gas and the like are used as a fuel, and in general, these gases are composed of a carbon monoxide, carbon or other hydrogen carbide. Therefore, in the presence of air, the combustion gas after burning a fuel includes a carbon dioxide gas, nitrogen monoxide gas, sulfur oxide gas or the like, in addition to a nitrogen gas and an oxygen gas. In recent years, a harmful gas such as carbon dioxide gas, nitrogen oxide or sulfur oxide is discharged into the atmosphere, consisting a social problem in a global environmental level in view of a global warming (greenhouse) effect or environmental pollution.
By the way, according to a treatment process for a nitrogen oxide gas and sulfur oxide gas, these gases have been already restricted within a range of legal constraint value along with the development of technology. However, in a treatment process for a carbon dioxide gas, since an amount of the carbon dioxide gas to be treated is large, a preferable means for solving such problem has not been still found.
Recently, a solvent of selectively absorbing a carbon dioxide from the exhaust gas has been proposed as means for treating a carbon dioxide gas from a gas discharged into the atmosphere after the combustion. This solvent makes use of the property of readily discharging a carbon dioxide when heating the solvent absorbing the carbon dioxide.
There are the following several problems in the means for treating a carbon dioxide with the use of the above solvent already proposed.
First of all, although the carbon dioxide is absorbed by contacting it with the solvent, because the contact time is not infinitely taken, it is difficult to always contact an exhaust gas to the solvent during an operation of thermal power plant. For this reason, a carbon dioxide gas component is not recovered and remains in the exhaust gas. As a result, there is the possibility of discharging the carbon dioxide gas component into the atmosphere.
Secondary, in a thermal power plant, a large volume of carbon dioxide is generated. For this reason, a large volume of solvent is required in order to recover the large volume of carbon dioxide, and as a result, a great much of thermal energy for heating the solvent is required.
Therefore, according to the conventional method, a cost spent for a carbon dioxide recovery system itself becomes very high, and hence, a cost for driving the recovery system is also increased.
Furthermore, in the case of viewing from different angle, the following proposals have been made. More specifically, a solar energy is used so as to generate hydrogen to be used as a fuel. Moreover, a water vapor is added to carbon dioxide so as to generate a mixed gas, and then, the mixed gas is circulated while the water vapor being condensed to separate a carbon dioxide. However, these proposals are still in a state of laboratory level, and therefore, it is difficult to realize a practical use.
A primary object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a thermal power plant which can effectively treat a carbon dioxide with the use of a carbon dioxide absorbing and discharging agent which has a property of absorbing the carbon dioxide by using a lithium substance when reaching a predetermined temperature and decomposing the reacted lithium carbonate when reaching a predetermined temperature.
Another object of the present invention is to provide a thermal power plant which effectively makes use of a thermal energy discharged from a carbon dioxide absorbing and discharging agent so as to improve a plant thermal efficiency of the thermal power plant.
These and other objects can be achieved according to the present invention by providing, in one aspect, a thermal power plant comprising:
an air compressor which compresses a sucked air to generate a high pressure air;
a gas turbine combustor operatively connected to the air compressor and adapted to supply a fuel to the high pressure air from the air compressor to generate a combustion gas;
a high pressure gas turbine operatively connected to the gas turbine combustor and adapted to perform an expansion working of the combustion gas from the gas turbine combustor and generate an exhaust gas;
a low pressure gas turbine operatively connected to the high pressure gas turbine and adapted to perform an expansion working of the exhaust gas from the high pressure gas turbine and generate an exhaust gas containing carbon dioxide; and
a carbon dioxide absorbing and discharging equipment located on an outlet side of the low pressure gas turbine, the carbon dioxide absorbing and discharging equipment being provided with a carbon dioxide absorbing and discharging agent having a property of absorbing the carbon dioxide contained in the exhaust gas supplied from the low pressure gas turbine and decomposing the absorbed carbonate by the exhaust gas supplied from the high pressure gas turbine, wherein a temperature of the gas turbine exhaust gas supplied from the high pressure gas turbine to the carbon dioxide absorbing and discharging equipment and a temperature of the exhaust gas supplied from the low pressure gas turbine to the carbon dioxide absorbing and discharging equipment are set to pre-determined ranges of values different from each other.
In preferred embodiments, the thermal power plant may further comprise a regenerator operatively connected to the carbon dioxide absorbing and discharging equipment and the air compressor and adapted to generate a heat by utilizing a carbon dioxide gas discharged from the carbon dioxide absorbing and discharging equipment as a heat source and to heat the high pressure air supplied from the air compressor to the gas turbine combustor, or may comprise a fuel heater operatively connected to the carbon dioxide absorbing and discharging equipment and the gas turbine combustor and adapted to heat the fuel to be supplied to the gas turbine combustor by using the carbon dioxide gas discharged from the carbon dioxide absorbing and discharging equipment as a heat source.
The thermal power plant may further comprises an exhaust gas heat recovery boiler operatively connected to the low pressure gas turbine exhaust gas side of the carbon dioxide absorbing and discharging equipment and adapted to generate a steam and a steam turbine plant which is driven by the steam generated from the exhaust gas heat recovery boiler, and a fuel heater may be also provided additionally.
A fuel heater is operatively connected to the carbon dioxide absorbing and discharging equipment and the gas turbine combustor and adapted to heat the fuel to be supplied to the gas turbine combustor by using the carbon dioxide gas discharged from the carbon dioxide absorbing and discharging equipment as a heat source.
The carbon dioxide absorbing and discharging equipment is provided with a heat exchanger for heating the carbon dioxide absorbing and discharging agent by using the exhaust gas from the high pressure gas turbine.
The carbon dioxide absorbing and discharging equipment is provided with a seal portion for sealing and circulating the carbon dioxide absorbing and discharging agent therein. The carbon dioxide absorbing and discharging agent is composed of a lithium substance having the property of absorbing the carbon dioxide contained in the exhaust gas from the low pressure turbine and decomposing an absorbed lithium carbonate by the exhaust gas from the high pressure turbine. A temperature of the gas turbine exhaust gas supplied from the high pressure gas turbine to the carbon dioxide absorbing and discharging equipment is set to approximately 700xc2x0 C., and a temperature of the exhaust gas supplied from the low pressure gas turbine to the carbon dioxide absorbing and discharging equipment is set to approximately 500xc2x0 C.
In another aspect, there is provided a thermal power plant comprising:
an air compressor which compresses a sucked air to generate a high pressure air;
a gas turbine combustor operatively connected to the air compressor and adapted to supply a fuel to the high pressure air from the air compressor to generate a combustion gas;
a high pressure gas turbine operatively connected to the gas turbine combustor and adapted to perform an expansion working of the combustion gas from the gas turbine combustor and generate an exhaust gas;
an intermediate pressure gas turbine operatively connected to the high pressure gas turbine and adapted to perform an expansion working of the exhaust gas from the high pressure gas turbine and generate an exhaust gas;
a carbon dioxide absorbing and discharging equipment located on an outlet side of the intermediate pressure gas turbine, the carbon dioxide absorbing and discharging equipment being provided with a carbon dioxide absorbing and discharging agent composed of a lithium substance having a property of absorbing the carbon dioxide contained in the exhaust gas supplied from the intermediate pressure gas turbine and decomposing the absorbed lithium carbonate by the exhaust gas supplied from the high pressure gas turbine; and
a low pressure gas turbine operatively connected to the carbon absorbing and discharging equipment and adapted to perform an expansion working of the exhaust gas from the intermediate pressure turbine.
In this aspect, substantially the same or similar preferred embodiments as or to those mentioned above in the first aspect may be applicable.
Further, the exhaust gas supplied from the intermediate pressure gas turbine to the carbon dioxide absorbing and discharging equipment is set so as to have a temperature of approximately 500xc2x0 C. and a pressure of about 2 ata.
In a further aspect of the present invention, there is provided a thermal power plant comprising:
an air compressor which compresses a sucked air to generate a high pressure air;
a gas turbine combustor operatively connected to the air compressor and adapted to supply a fuel to the high pressure air from the air compressor to generate a combustion gas;
a high pressure gas turbine operatively connected to the gas turbine combustor and adapted to perform an expansion working of the combustion gas from the gas turbine combustor and generate an exhaust gas;
a low pressure gas turbine operatively connected to the high pressure gas turbine and adapted to perform an expansion working of the exhaust gas from the high pressure gas turbine and generate an exhaust gas containing carbon dioxide;
a plurality of carbon dioxide absorbing and discharging equipments located on an outlet side of the low pressure gas turbine, each of the carbon dioxide absorbing and discharging equipments being provided with a carbon dioxide absorbing and discharging agent having a property of absorbing the carbon dioxide contained in the exhaust gas supplied from the low pressure gas turbine and decomposing the absorbed carbonate by the exhaust gas supplied from the high pressure gas turbine; and
a change-over system operatively connected to the carbon dioxide absorbing and discharging equipments and adapted to change over the carbon dioxide absorbing and discharging equipments.
In this aspect, substantially the same or similar preferred embodiments as or to those mentioned above in the first aspect may be applicable.
Further, the change-over system may comprise: a first high temperature turbine exhaust gas supply pipe including a valve for supplying the exhaust gas from the high pressure gas turbine to a first carbon dioxide absorbing and discharging equipment; a first supply pipe for the low pressure gas turbine, which supplies the high pressure gas turbine exhaust gas from the first carbon dioxide absorbing and discharging equipment to the low pressure gas turbine; a second low temperature turbine exhaust gas supply pipe including a valve for supplying the exhaust gas from the low pressure gas turbine to the second carbon dioxide absorbing and discharging equipment; a second high temperature turbine exhaust gas supply pipe including a valve for supplying the exhaust gas from the high pressure gas turbine to a second carbon dioxide absorbing and discharging equipment; a second supply pipe for the low pressure gas turbine, which supplies the high pressure gas turbine exhaust gas from the second carbon dioxide absorbing and discharging equipment to the low pressure gas turbine; and a first low temperature turbine exhaust gas supply pipe including a valve for supplying the exhaust gas from the low pressure gas turbine to the first carbon dioxide absorbing and discharging equipment.
According to the various aspects of the present invention mentioned above, the thermal power plant includes the carbon dioxide absorbing and discharging equipment which is filled up with the carbon dioxide absorbing and discharging agent for treating carbon dioxide. The carbon dioxide absorbing and discharging agent has a property of absorbing carbon dioxide contained in the gas turbine exhaust gas discharged from the gas turbine plant at a temperature of about 500xc2x0 C. and decomposing the absorbed lithium carbonate at a temperature of about 700xc2x0 C. The agent is composed of lithium substance as a main component in order to make low a concentration of the carbon dioxide. Thus, it is possible to contribute to a prevention for global warming effect and environmental pollution.
Further, the thermal power plant according to the present invention includes the other means, such as regenerator, which uses a turbine exhaust gas having a low concentration of carbon dioxide from the carbon dioxide absorbing and discharging equipment and heats the high pressure air supplied from the air compressor to the gas turbine combustor or the fuel introduced into the gas turbine combustor. Thus, it is possible to effectively use a thermal energy and to improve a plan heat efficiency.